Epitaxy refers to the deposition by growth of an overlayer on a crystalline substrate where the overlayer is in registration with the substrate. The substrate surface acts as a seed layer for the growth. Epitaxial materials may be grown from gaseous or liquid precursors. Because the substrate surface acts as a seed crystal, the epitaxial growth locks into one or more crystalline graphic orientations of the crystalline substrate. Epitaxial growth is widely used in the manufacture of integrated circuitry and may be fabricated on various types of crystalline—base materials, for example, semiconductor substrates, and of various epitaxial materials. As an example, an epitaxial silicon growth may be provided on a silicon substrate, such as bulk silicon substrates, and silicon on insulators (SOI) substrates. However, an epitaxial grown material tends to form crystalline defects, known as dislocations and stacking faults, during growth, at confined side edges of the grown material. These crystalline defects can result in undesired charge leakage within or between devices fabricated from the epitaxial material, or undesired electron-hole charge recombination sites which reduces device electrical efficiency. If the grown epitaxial material is used in forming an electro-optical photonic device, such as a photodetector, these defects may cause dark current and also reduce the efficiency of the photonic device.
One solution to the dislocation and stacking fault problem in epitaxially grown materials has been to use a particular crystal orientation of an underlying silicon layer on which the epitaxial layer is grown. For example, U.S. Pat. No. 7,906,830 describes an integrated structure in which a silicon substrate orientation is changed to “111” so that silicon crystal orientation along a confined sidewall is in the “100” direction. Although the wafer reorientation described in U.S. Pat. No. 7,906,830 can reduce dislocations and stacking faults, it is often undesirable to orient the wafer in this manner for other technical reasons, such as optimizing performance of fabricated transistors and other structures which may be formed on the substrate.
A method and resulting structure which provide an epitaxial growth of an electro-optical photonics device, such as a photodetector, with fewer dislocations and stacking faults and which does not require a particular crystal orientation of the substrate is desired.